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Solution: Distinct Subsequences

Explore how to apply dynamic programming to find the number of distinct subsequences of a string s that match another string t exactly. Understand the use of a 1D DP array to optimize space and the steps to build the solution by iterating strings in reverse. This lesson helps you implement a time-efficient approach with O(m x n) complexity and minimal memory use.

Statement

Given two strings, s and t, determine how many distinct subsequences of s match t exactly.

Note: A subsequence is formed by deleting zero or more characters from s without changing the relative order of the remaining characters.

You may assume the result will always fit within a 3232-bit signed integer.

Constraints:

  • 11 \leq s.length, t.length 1000\leq 1000 ...